In the Customer/Supplier Invoice view click to open the Other Info tab, then Add an item to the Tax list near the bottom of the form.

AFAIK all taxes, although defined for every line item (or some of the line items), will be applied to the total sum of the invoice (or total sum of all line items that has that invoiced defined).  So, Marek's way to add Tax also works.

The difference is that Marek's way will make the tax defined in each line (i.e. you tax on each item), and adding it to the Tax list will NOT make the tax defined in each line (i.e. you tax on the invoice total).

you need to add this additional tax on each line and then have sum. Amount can be little different due to rounding.

Marek Mosiewicz

http://consultantodoo.com